(RHSA-2010:0126) Important: kvm security and bug fix update

KVM (Kernel-based Virtual Machine) is a full virtualization solution for
Linux on AMD64 and Intel 64 systems. KVM is a Linux kernel module built for
the standard Red Hat Enterprise Linux kernel.

A flaw was found in the way the x86 emulator loaded segment selectors (used
for memory segmentation and protection) into segment registers. In some
guest system configurations, an unprivileged guest user could leverage this
flaw to crash the guest or possibly escalate their privileges within the
guest. (CVE-2010-0419)

The x86 emulator implementation was missing a check for the Current
Privilege Level (CPL) while accessing debug registers. An unprivileged
user in a guest could leverage this flaw to crash the guest.
(CVE-2009-3722)

This update also fixes the following bugs:

With Red Hat Enterprise Virtualization, the virtio_blk_dma_restart_bh()
function was previously used to handle write errors; however, a bug fix
provided by the RHSA-2009:1659 update meant that read errors would also
have to be handled by this function. The function was not updated for this,
causing read errors to be resubmitted as writes. This caused guest image
corruption in some cases.

Additionally, the return values of the bdrv_aio_write() and bdrv_aio_read()
functions were ignored. If an immediate failure occurred in one of these
functions, errors would be missed and the guest could hang or read
corrupted data. (BZ#562776)

All KVM users should upgrade to these updated packages, which contain
backported patches to resolve these issues. Note: The procedure in the
Solution section must be performed before this update will take effect.